The world’s longest continental range walls South America
The Andes run 8,900 kilometres down South America's western edge, the longest continental mountain range on Earth and the highest outside Asia. Averaging about 4,000 metres, they lift cities such as La Paz and Bogotá onto high plateaus, and Ecuador's Chimborazo sits farther from Earth's centre than any other point on the surface.
The range is 200 to 700 kilometres wide, broadest between 18° and 20° south, and splits into parallel ranges separated by depressions and high plateaus; the Altiplano is second only to Tibet among the world's high plateaus. Argentina's Aconcagua, about 6,961 metres, is the tallest peak, and the planet's highest volcanoes, among them Ojos del Salado on the Chile–Argentina border, rise here. Geographers divide the chain into Southern Andes in Argentina and Chile, Central Andes in Bolivia and Peru, and Northern Andes in Colombia, Ecuador and Venezuela, where it forks into three branches.
Most scholars trace the name to Quechua anti, east, as in Antisuyu, the eastern quarter of the Inca Empire, though some prefer the older Aymara anta, copper. Cordillera, the Spanish word for such chains, comes from cordel, rope. The Andes belong to the American Cordillera, the nearly unbroken mountain backbone of the Americas and Antarctica, and the peaks of the Antarctic Peninsula, across the 1,000-kilometre Drake Passage, appear to continue them.
The mountains exist because the Nazca Plate, joined farther south by a slice of the Antarctic Plate, keeps diving under the continent's own plate. The modern range began with rifting as Pangaea broke up in the Triassic and took its present shape during the Cretaceous, as older rocks to the east were uplifted, faulted and folded. That subduction still drives great earthquakes, such as the 2010 Maule quake of magnitude 8.8 and the 2015 Illapel quake of 8.2, and it feeds active volcanoes grouped into four zones separated by quiet gaps.
Sharp climatic contrasts, from humid cloud forest on eastern slopes to the dry Altiplano and the glaciated southern summits, shaped where people settled, including Bogotá, Cusco, La Paz and Quito. Aruba, Bonaire and Curaçao were once taken for sunken northern Andean peaks, but newer geology suggests the plate boundary there is more complicated. Andean condors, the largest flying birds by combined weight and wingspan, ride the updrafts on wings up to 3.3 metres across.
Source: Andes
